There are known on the market various types of disc sanding or grinding machines to perform cleaning, polishing, grinding or brushing operations on substantially flat surfaces made of stone, wood, metal, glass or composite materials.
These machines generally comprise one or more discs or plates (to which different tools, with different degrees of abrasion, are fitted), which are rotated around their axis, around an orbit, or both, and which, in contact with a surface, perform one of the aforesaid machining operations.
Portable grinding machines, angular or axial, are generally provided with a single disc of limited dimensions (generally less than 250 mm in diameter) connectable to a machine body that, as well as containing a motor, is often also shaped to act as handle for at least one of the operator's hands.
However, these prior art portable grinding machines, when used on substantially flat surfaces, have some limits and drawbacks.
In fact, they have no base and consequently all translations of the tool, both parallel and perpendicular to the surface, are controlled by the operator performing the machining operation.
Above all, during sanding or grinding operations on flat surfaces such as floors, walls, but also beds or the like, it is important that the contact pressure exerted by the tool is as constant as possible and that it maintains a given angular position with respect to the surface (generally with an angle between 0° and 1°).
With prior art portable sanding and grinding machines this is practically impossible even for the most skilled operators as, without the aid of any reference, these parameters are controlled and managed in an entirely manual manner based on the sensitivity of the operator's limbs.
Moreover, handling of these portable devices is made even more difficult by the torque that is transmitted to the body of the machine by the tool when it comes into contact with the surface to be machined.
Therefore, the operator, who already has to oppose rotation of the machine body, also has the difficult task of correctly metering the pressure of the tool and of correcting its angle with precision.
Consequently, surfaces machined with these devices always have various imperfections, such as ridges, dips and areas with different degrees of roughness.
Moreover, with these prior art machines, machining operations on flat surfaces, even of limited dimensions, requires considerable mental and physical effort by the operator.
Similarly to portable machines, semi-portable sanding machines also comprise one or more rotating abrasive discs, but unlike the former, given the larger dimensions and increased weight, these are almost always mounted on a base that facilitates their translation on the surface to be machined.
These bases are typically provided with a pair of wheels placed side by side on the same side of the machine as the handle used to guide it during machining.
Machines configured in this manner also have some limits and are therefore subject to improvement.
The weight of these machines is discharged on three areas of contact with the surface: two on the two supporting wheels and one on the machining disc or discs.
During machining operations of sanding, grinding, brushing or polishing etc., the pressure exerted by the tool is a function of the portion of weight that is discharged to the ground, which in turn depends on the force with which the operator presses on the guiding handle while moving the machine.
In practice, to allow the machine to move forward, the operator must exert a thrust in a direction substantially parallel to the surface to be machined (floor, shelf, etc.) and also press (use leverage) on the handle to discharge part of the weight transmitted to the tool and thereby reduce friction.
Just as in the case of portable machines, also in this case it is difficult or even impossible to maintain a constant thrust on the handle in order to maintain a constant pressure exerted on the surface to be sanded/polished.
In the same way, the angular position of the tool is almost never constant as it is subject to a deformation, caused by compression on the surface, which is more or less accentuated as a function of the tool material (metal, resins, etc.).
With prior art portable and semi-portable sanding machine it is therefore difficult to obtain a machined surface without defects, which are more accentuated when the operator lacks experience.
In this context, the object of the present invention is to provide a base for sanding machines, grinding machines or the like, which overcomes the problems of the prior art described above.